Shot in the dark here, I think its because she's hyper-active and spastic like a small dog. So she has small dog ears. But she's also a cat, because I assume a person with a personality of Temmie online has to have like a goddamn billion cats IRL, so she has cat ears as well. Then add on the personality of The penguin of Doom and give her 1337 speak and there we go. She's the embodiment of the crazy girl from middle school.